Treatment of zinkiferous ores.



pm ears re ro JAMES HYNDES GILLIES AND PERCY MCPHERSON GILLIES, OF EASTCAMBERWELL, VICTORIA, AUSTRALIA.

TREATMENT OF ZINKIFEROUS ORES.

No Drawing.

To all whom it mag concern:

Be it known that we, JAMES HYNDEs GIL- LIES and PERCY MGPHERSON GILLIES,subjects of the King of Great Britain, residing at Craigie Var, MontAlbert Road, East Camberwell, in the State of Victoria, Coninionwealthof Australia, have invented certain new and useful Improvements inConnection with the Treatment of Zinkiferous Ores, of which thefollowing is a specification.

This invention refers to the treatment of zinkiferous ores and moreparticularly to complex ores containing zinc and other metals such asoccur on the west coast. of Tasmania and in other parts of the world.These ores contain zinc blende and other sulfids in association, and maybe treated fresh from the mine or in the form of tailings, concentratesand the like for the recovery of their several valuable contents.

Hitherto, attempts have been made to treat complex zinkiferous ores byordinary leaching processes, in which the ores are very finely crushed,calcined to a dead roast, and treated with acid to dissolve the zinccontents. The solution thus obtained is electrolyzed to recover thezinc. It has been found difiicult by this means to obtain the zinc inthe roasted material in a condition readily soluble in acid, and thesolution is, further, liable to be fouled with iron, copper andmanganese, as well as arsenic, antimony, cadmium, et cetera.

' According to our invention We utilize a process made up of acombination of metallurgical operations each in itself more or less wellknown, but not hitherto known and used, in combination, for the purposesof our invention.

We provlde by our process, which includes dry and wet methods ofextraction, certain improvements wherein the preliminary very finecrushing and dead roasting is avoided, and wherein the zinc is obtainedas a fume in a condition readily soluble in acid and entirely free fromiron, copper and manganese. The solution obtained is purified and isthen treated in electrolytic cells for the recovery of metallic zinc.

In carrying our process into effect, the ore is coarsely crushed to passthrough say a inch screen and is partially desulfurized by roasting.With ores yielding in the crushing operation an excessive amount offines,

Specification of Letters Patent.

Application filed January 22, 1917.

Patented Apr. 9, 1918.

Serial no. 143,819.

may occur through losses of solution during working operations.

The roasted material is mixed with a proportion of' carbonaceousmaterial, preferably coke and after being damped with about 20% of waterby weight, it is fed into a fuming furnace of the type having aperforated grate, through which a low pressure air blast is passed.

Zinc and lead in the ore are in this furnace volatilized and are drawnoff in the form of fume which consists mainly of zinc oxid (ZnO) andlead sulfate (PbSUJ. This fume is cooled and collected in a baghouse orother fume collecting apparatus.

The sintered mass remaining in the furnace and known as clinker willcontain gold, silver and copper values, as well as any zinc notvolatilized. This is withdrawn from the furnace and snielted in anelectric or suitable blast furnace with the requisite fluxes to obtainthe copper, silver and gold in the form of a matte, and to volatilizezinc and lead that has escaped the fuming operation, such volatilizedfume being collected in the main baghouse system.

In the treatment of the complex zinkiferous ores of Tasmania whichcontain zinc, lead. copper, arsenic, antimony, gold and silver values,the collected fume, we have found, consists mainly of zinc oxid and leadsulfate, with small quantities of arscnical and other volatilemetalliccompounds which, in the electrolytic treatment for the recoveryof zinc, act detrimentally to the efficient work ing of the process andshould therefore be l'eliter of the solution sat;

solution is then allowed to stand in order to settle out the leadsulfate which is collected and smelted, the amount of free acidremaining after treatment being from 1-; to 2 per cent.

This slightly acid solution containing zinc sulfate, with the salts ofvolatile metals such as arsenic, and antimony, is heated to about 80Centigrade and treated in suitable apparatus with sulfureted hydrogen (H5) gas to precipitate as sulfids these impurities. After settling, theclear solution is decanted and the sulfid sludge or precipitate filteredin a vacuum filter composed of porous tiles covered with a thin layer ofdiatomaceous earth.

In the event of cadmium being present it is advisable to pass thesolution over granulated zinc before H 8 treatment to remove the bulk ofthe cadmium, minute traces of which in the electrolyte do notseriouslyaffeet the deposit-ion and quality of the zinc, whereas evenvery minute quantities of arsenic and antimony are likely to spoil thezinc deposit.

The purified zinc sulfate solution is then passed through electrolyticcells, in which zinc is deposited and a corresponding amount of H SOliberated as free acid. The acidified solution is then again used totreat fresh batches of fume and so on cyclically.

Zinc plates lead as anodes, current densit are used as cathodes and pureand we have found that a of 25 to 30 amps. per square foot of catho esurface yields the best re sults. A an role cell. for use with this partof our process is described. in the specification attached to ourCommonwealth of Australia Patent 16698, dated the 30th day of June,1915.

To insure an even deposition of zinc, it is advantageous to use in thecells a colloidal addition agent such as gum arabic. we have found thatif from one half to one gram of the addition a e -t he adderv per.iactary results are obtained.

In the recovery of metallic zinc by electrolysis it isof primeimportanceto obtain a zinc sulfate solution as nearl free from arsenical and otherlike impurities as possible. From an impure solution, the impurities aredeposited with the zinc and electrolysis is retarded, if not entirelysuspended, when the solution becomes about 3 per cent. aci-fl But if theimpurities are removed as herein explained, before electrolysis, we rindthat the latter will proceed efficiently until the solution approaches1042 per acid. This acid solution is incense then pumped to a dissolverand is almost neutralized with a supply of fresh fume. By depositingzinc until the solution becomes strongly acid, the need for removing theacidified solution less frequent, with consequent savings in workingcosts. Thus, apart from the great advantage of obtaining a pure oralmost pure zine deposit, we

hare in our process a longer continuity of electrolytic action and aresulting larger quantity of free acid with which to treat more fume.

l-lavingnow described our inventioinwhat we claim as new and desire tosecure by Letters Patent 1. The process of treating complex sulfid oresfor the covery of zinc which consists in fuming the crushed andsemiroasted ores, treating the fumed zinc oXid and lead sulfate with HSO solution to dissolve the zinc oXid, purifying the zinc sulfatesolution so obtained with H 8 gas to precipitate the impurities assulfids and electrolyzing the purified zinc solution, as specifled.

2. In the treatment of complex sulfid ores of the kind indicated, fumingthe zinc and lead from the crushed and semi-roasted ore in a furnace,retreating the clinker with fluxes to recover precious metals and copperand fuming off any remaining zinc, treating the zinc and lead fume withH 80 soludissolve the Zn() and the resulting 'eiectrolyzing the purifiedsolution to deposit metallic zinc, as herein set forth.

In the treatment of complex sulfid ores for the recovery of the valuablecontents, the process which consists in coarsely crushing and partiallydesulfurizing the ore, collecting and treating the fines separately to asulfatizing roast and agglomerating the same, fuming the semi-roastedores in a furnace, retreating the furnace clinker, fltii'igg; the zincand lead fume with sulid solution to obtain zire sulfate in .tion andpurifying the same with gas to recover the arsenical and other likeimpurities therein prior to the solution being submitted toelectrolysis, and for the purposes specified.

In witness whereof, we have hereunto signed our names in the presence,of two subscribing witnesses.

JAMES HYNDES GILLIES. PERCY MGPHLRSON GILLIES.

W itnesses it. hl. Nnw'rorr, l). tinow rn'nn.

